1. Field of the Invention
The present invention relates to fibre channel switches, and more particularly to using distributed Name Server data in multi-module fibre channel switches.
2. Background of the Invention
Fibre channel is a set of American National Standard Institute (ANSI) standards which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel fabric devices include a node port or “N_Port” that manages fabric connections. The N_port establishes a connection to a fabric element (e.g., a switch) having a fabric port or F_port. Fabric elements handle routing, error detection, recovery, and similar management functions.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware. The fibre channel switch provides circuit/packet switched topology by establishing multiple simultaneous point-to-point connections.
A fibre channel switch is a multi-port device where each port manages a simple point-to-point connection between itself and its attached system. Each port can be attached to a server, peripheral, I/O subsystem, bridge, hub, router, or even another switch. A switch receives a message from one port and automatically routes it to another port. Multiple calls or data transfers happen concurrently through the multi-port fibre channel switch.
Fibre channel switches may use multiple modules (also referred to as “blades”) connected by fibre channel ports. Conventionally, a multi-module switch is integrated as a single switch and appears to other devices in the fibre channel fabric as a single switch.
Fibre Channel Generic Services (FC-GS-3) specification describes in section 5.0 various fibre channel services that are provided by fibre channel switches including using the “Name Server” to discover fibre channel devices coupled to a fabric.
A Name server provides a way for N_Ports and NL_Ports to register and discover fibre channel attributes. Request for Name server commands are carried over the Common Transport protocol, also defined by FC-GS-3. The Name server information is distributed among fabric elements and is made available to N_Ports and NL_Ports after the ports have logged in.
Various commands are used by the Name Server protocol, as defined by FC-GS-3, for registration, de-registration and queries.
Fiber Channel Switched Fabric (FC-SW-2) specification describes how a Fabric consisting of multiple switches implements a distributed Name Server.
The current fibre channel standards or conventional techniques do not provide an efficient way to share Name Server data among the blades, such that the multi-module switch appears to the rest of the fabric as a single switch.
In addition, the Fiber Channel standards do not provide any method for sharing Name Server information on multiple independent switch modules that are part of the same switch.
Therefore, what is required is a process and system that allows multiple switch modules to implement Name Server commands so that the multiple switch modules appear as one switch to the rest of the Fabric.